Android phone can’t make or receive calls
When an Android phone cannot receive calls, or they are going straight to voicemail without ringing the phone, the phone calls are not received by the mobile phone’s SIM card.
In some cases, it is also possible that the phone is able to place phone calls to other phone numbers, but cannot receive incoming calls.
Check phone network service coverage
The first step is to make sure that the phone is connected to the mobile phone network, by having a look at the network service icon on the top right corner of Android’s screen.
Fix network issues and select carrier
Start by restarting the mobile phone before troubleshooting the network issues.
After that, go to settings > more > cellular networks > network operators > choose a network operator > search networks.
From there, select the carrier to which you should connect, which usually is the one at which you have bought your SIM card.
After having connected to the network operator, try to place a phone call, this should then be working.
Check block list
If the number that is trying to reach cannot make your phone ring, but you are able to call him, try to check that the phone number hasn’t been added to the block list.
Open the phone app, and tap the three dots menu on the top right of the application to open settings selection.
There, open the blocked numbers list, and check that the number trying to reach you hasn’t been blocked.
If it has been blocked, unblock it from that list, and the problem should be solved.
Do not disturb modem
It might be the case the phone has been set in the do not disturb mode, and that all incoming calls are blocked from reaching your phone number, and instead are sent directly to the voicemail.
Open the settings > do not disturb menu. From there, make sure that the calls are allowed even when the phone is set in do not disturb.
Reset network settings
If your Android phone allows it, another option is to reset the network settings.
To do so, go to settings > backup and reset > reset network settings.
Factory reset phone
If nothing worked, and you are still able to make outgoing calls, but cannot receive calls, the last step before contacting your network provider is to perform a factory reset.
However, before doing so, make sure that nobody at all is able to reach you, and that the contact that cannot make calls to you is actually dialing the right number.